1. Field of the Invention
The present invention relates to methods for treating brassicaceous vegetables capable of reducing the formation of a nasty smell characteristic of vegetables belonging to Brassicaceae and methods for producing brassicaceous vegetable beverages.
2. Related Art Statement
These kinds of vegetables, that is, brassicaceous vegetables typical of cabbages, are rich not only in vitamin U having a nutritional value, but also in vitamin C and dietary fiber. In addition, they have been recently notable, in particular, as material for producing vegetable juices and the like, since it has been found that they have an effect on inhibiting cancer cells and preventing gastric ulcer.
When vegetable beverages are produced by squeezing vegetables, processes of a chopping step followed by a squeezing step are in general carried out. In particular, in the case of brassicaceous vegetables, since allyl isothiocyanate (AITC) contributing to discomfort odor is generated by activating enzymes upon chopping them, the chopping step is a problematic step in producing vegetable juices to be readily drunk.
For example, Japanese Patent Laid-open Publication Hei 10-42841 notices that a chopping treatment, such as shredding, results in activation of enzymes responsible for the formation of a nasty smell, and discloses a treating method for reducing the formation of a nasty smell by the addition of vitamin C at the step of chopping vegetables, and furthermore squeezing the chopped vegetables before concentration.
As described above, however, when vitamin C is added at the chopping step, and subsequent steps of heating and squeezing are carried out, vitamin C is necessary to add again in order to adjust the acidity after squeezing, since heating will cause the decomposition of vitamin C. This means that expensive vitamin C must be used in a large amount.
In consideration of such problems, the present invention is intended to provide a new method for treating brassicaceous vegetables and a method for producing brassicaceous vegetable beverages which do not allow a characteristic discomfort odor to generate upon treating brassicaceous vegetables typical of cabbages, and in addition, enables to reduce the amount of expensive vitamin C to be used.
In order to solve such problems, the present invention provides a treatment of heating brassicaceous vegetables before chopping them. Since the heat treatment before chopping can result in deactivating enzymes, enzymes causing the formation of components of a discomfort smell during the chopping step can not be activated, and thereby the generation of a nasty smell characteristic of brassicaceous vegetables can be eliminated.
For heating at this step, it is preferable that heating is carried out such that the temperature of the vegetables is allowed to maintain in the range of about 80 to 95xc2x0 C. Means for heat treatment preferably take means of increasing the temperature of the vegetables by xe2x80x9csteaming,xe2x80x9d that is, by steam.
If the temperature of the vegetables is below 80xc2x0 C., it may be likely that enzymes are not fully deactivated, whereas if the temperature rises over 95xc2x0 C., it may be likely that the thermal decomposition of a useful component, vitamin U, is increased. However, the requirement for the treating temperature is influenced by the pressure, atmosphere, and the like, and therefore similar effects can be expected, even if the temperature changes by about 5xc2x0 C. below or above the temperature described above. In addition, heating by xe2x80x9csteamingxe2x80x9d allows heat treatment with retaining the freshness of the vegetables, and furthermore, does not cause smell resulting from heating, such as a burnt smell, even if the temperature of the vegetables is increased to 95xc2x0 C. Heat treatments, in general, involve blanching (boiling). Blanching causes the contents of the vegetables to leach out into the boiling water, resulting in reduced Brix (soluble solid components), whereas steaming is better in that enzymes can be deactivated without reducing Brix (soluble solid components).
In the case of heat treating whole cabbages, for example, it may be likely that the deactivation of enzymes becomes insufficient in places due to difficulties in heating them uniformly. Increasing the heating temperature in order to avoid such partial deactivation will lead to the thermal decomposition of the contained vitamin U. Now, the present invention provides optional pretreatments, such as removing core portions containing particularly a large amount of isothiocyanates such as AITC, making cuts into vegetables, making leaves apart, or the like. Pretreatments like these can suppress the activation of enzymes to a minimum, and apply uniformly and efficiently heat to vegetables such as cabbages and the like, even if they do not readily transfer heat to their core portions.
Furthermore, it is preferable that vegetables which has been heat treated as described above are subjected to a treatment by contacting, after chopping (including shredding, grinding and the like) and squeezing, the squeezed fluid with an anion exchanger provided with the structure comprising mixing at least one or more inorganic anions and at least one or more organic acids to form ionic bonding, that is, an ion exchanger in which inorganic anions and organic acid(s) are forced to form ionic bonding to the ion-exchanging groups. Even if any component causing a nasty smell still remains in the squeezed fluid, such a component can be removed by this ion-exchange treatment. Although brassicaceous vegetables are known to contain a high level of nitrate, this treatment can be intended to reduce nitrate ion. Furthermore, it is possible that by the treatment with such an anion exchanger, components beneficial to the taste and health, such as minerals and the like, are maintained at the same time.
Treated fluid obtained by the treatments according to the present invention may be optionally subjected to treatments such as filtration, adjustment of the concentration, sugar content, and pH, sterilization, and the like, and have various applications such as beverages and other drinking, cooked food, seasonings, and the like.